1. Field of the Invention
The present invention relates to a snap-fastener, and more particularly to a snap-fastener having locking mechanism so that a male member and a female member do not disengage accidentally.
2. Description of the Related Art
With a known snap-fastener of this type (German Patent No. 3742007C1), an engaging portion of a male member extends forwardly at an acute angle with respect to an axis of the snap-fastener, while a corresponding portion of a female member extends similarly diagonally but along the axis. The engaging portion and the corresponding portion are temporarily resiliently deformed merely by pressing male and female parts against each other, thus they are engaged. The both member of the snap-fastener can be separated in the same manner.
Another type of snap-fastener is disclosed in Japanese Laid-Open Publication No. Hei 7-42327. According to this publication, with locking elements disposed movably in a central engaging space toward the axis in the female part, a male member is secured to a female member. The locking elements are composed of a pair of halves and a resilient member bridging ends of the halves, and the halves are normally urged to close to each other by the resilient member. In the middle of the halves, there provided projections in a shape of isosceles triangle in a plan view, slanting surfaces of which are urged to close to each other. The male member is prevented from being released from the female member, with the two halves contacting a neck of an engaging head of the male member at its under side, while being locked. When an opening device if inserted toward the slanting surfaces of the projections, the projections are moved outwardly against the resiliency of the resilient members. A gap between the halves becomes greater than the diameter of the engaging heads due to the movement, thus locking between the male part and the female part are released so that the male and female parts can be disengaged.
As described above, the conventional snap-fasteners have defect that the male and female parts can be disengaged easily by any person. With the locking snap-fasteners disclosed in the foregoing publications, their structures are relatively complicated which means high manufacturing cost, and further due to the locking element having the foregoing structure, the required space would necessarily be large and the snap-fastener would be voluminous as a whole.